| 摘要 |
PURPOSE:To dispense with a precise and complicated process of measurement of a magnification error on the occasion of assembly and adjustment and to make it possible to cope with a change with time, by providing a means of detecting an error in the magnification of a mark observing system by observing, through the observing system, a reference mark whose size is known correctly. CONSTITUTION:Prior to the alignment of a reticle 1 and a wafer 2, a control circuit 13 moves a mirror 9 above a transparent portion (a) of the reticle 1. Under the condition, a polygon mirror 7 is rotated and a reference mark of a glass plate 18 is scanned by a laser beam so as to measure the size of a portion (c) on the basis of the mark on the glass plate 18. Mark (b) denotes the direction of scanning by the laser beam. The measurement of the size of this reference mark is conducted when the system is delivered, when it is subject to a periodical inspection, or when occasion calls. It may be conducted also every time when the system is started. When the size measured as described above is found to be c', for instance, it is known that the magnification error of the given optical system is c/c'. |
